Ultra-low temperature heat energy recycling system and method based on advanced thermodynamic cycle

Abstract

The present application relates to the technical field of advanced thermodynamic cycle, in particular to a very low temperature heat energy recycling system and method based on advanced thermodynamic cycle. It comprises: a heat source guide and heat absorption unit for pretreating low temperature heat source and transmitting heat data to mixed working medium through a heat exchange module; a heat energy conversion and working medium compression unit for receiving heat data to convert heat data and compress working medium; a heat recovery and heat release unit for reducing the temperature of working medium through constant pressure heat exchange and transferring heat data to a Rankine cycle to do work; and a working medium expansion and compression energy recycling and refrigeration unit for adiabatic expansion of high pressure and low temperature working medium to further reduce the temperature and pressure of working medium and provide cooling energy to the system. The present application can maximize the recycling and utilization of waste low temperature heat energy by using advanced thermodynamic cycle, especially high efficiency energy conversion mechanism in very low temperature range.

Description

Technical Field

[0001] This invention relates to the field of advanced thermodynamic cycle technology, and more specifically, to an ultra-low temperature heat energy recovery and utilization system and method based on advanced thermodynamic cycles. Background Technology

[0002] Due to the low energy density and high utilization cost of low-temperature thermal energy, early traditional energy conversion technologies treated most gas-phase thermal energy below 150℃ and liquid-phase thermal energy below 90℃ as waste energy, such as kiln exhaust gas, power plant boiler flue gas, and factory hot wastewater. Furthermore, the exchange and discharge of this energy during production requires large amounts of cooling media and cooling energy, such as circulating water, refrigerants, and refrigeration equipment, resulting in both energy waste and energy consumption—approximately one-third or more of the factory's total energy consumption. Currently, most research institutions claim to have achieved numerous results in the application of hot air down to 90℃ and hot water down to 60℃, such as ORC organic working fluid low-temperature waste heat power generation. Taking hot air utilization as an example, according to the second law of thermodynamics, assuming the primary heat source temperature is 1050℃ and the exhaust temperature after initial utilization is 150℃, the efficiency limit for initial utilization is 68.1%. After utilizing a secondary heat source at 150℃, the secondary exhaust temperature is 90℃, and the efficiency limit for secondary utilization is 14.2%. If the energy is reused a third time, the efficiency will be even lower, thus rendering it useless. Therefore, providing ultra-low temperature heat energy recovery and utilization systems and methods based on advanced thermodynamic cycles is an important achievement for improving energy utilization efficiency and reducing process carbon emissions. Summary of the Invention

[0003] The purpose of this invention is to provide an ultra-low temperature heat energy recovery and utilization system and method based on advanced thermodynamic cycles, so as to solve the problems of low energy utilization efficiency, insufficient waste heat recovery and high carbon emissions of the system mentioned in the background art.

[0004] To achieve the above objectives, on the one hand, the present invention aims to provide an ultra-low temperature heat energy recovery and utilization system based on an advanced thermodynamic cycle, comprising:

[0005] A heat source guiding and heat absorption unit pre-treats a low-temperature heat source and transmits the heat data to the working fluid through a heat exchange module.

[0006] A heat energy conversion and working fluid compression unit receives heat data and performs heat data conversion and working fluid compression.

[0007] A heat recovery and heat release unit, which combines Rankine cycle to transfer heat data and perform work externally;

[0008] The working fluid expansion pressure energy recovery module performs adiabatic expansion of the high-pressure and low-temperature working fluid to further reduce the temperature and pressure of the working fluid and provide cooling energy to the system.

[0009] The adiabatic expansion pressure energy recovery unit expands the low-boiling-point working fluid from high pressure and low temperature to low temperature and low pressure, converting pressure energy into cooling energy.

[0010] A working fluid mixing and pressurization unit, wherein the working fluid mixing and pressurization unit mixes working fluids in different states and pressurizes the mixed working fluid;

[0011] The monitoring and control unit predicts, adjusts and optimizes various processes of the heat recovery system in real time through intelligent optimization and coordinated control, and further optimizes the viscosity correction factor and the friction factor affected by the deposits on the inner surface of the pipe by incorporating them into the intelligent optimization process.

[0012] As a further improvement to this technical solution, the heat source guiding and heat absorption unit includes a heat source pretreatment module and a constant pressure heat absorption module;

[0013] The heat source pretreatment module collects low-temperature heat sources and pretreatments them.

[0014] The constant pressure heat absorption module transfers heat from the low-temperature heat source to the mixed organic working fluid through a heat exchange module.

[0015] As a further improvement to this technical solution, the heat energy conversion and working fluid compression unit includes a throttling flash evaporation module and an adiabatic compression module;

[0016] The throttling flash evaporation module reduces the temperature and pressure of the mixed organic working fluid through isentropic throttling, thereby transferring the heat energy absorbed by the mixed organic working fluid to the low-boiling-point gas phase working fluid.

[0017] The adiabatic compression module pressurizes the low-boiling-point gaseous working fluid, increasing its temperature and pressure.

[0018] As a further improvement to this technical solution, the heat recovery and heat release unit combines Rankine cycle to transfer heat data, including constant pressure heat exchange and an additional Rankine cycle system.

[0019] The heat recovery and heat release unit includes a low-boiling-point working fluid in a constant-pressure heat exchange module that transfers heat data to an external Rankine cycle working fluid through partial condensation.

[0020] The heat recovery and heat release unit includes constant-pressure heat exchange in a constant-pressure heat exchange module to reduce the temperature of the working fluid and transmit heat data to the Rankine cycle working fluid.

[0021] The heat recovery and heat release unit includes the use of an additional Rankine cycle working fluid to perform work externally;

[0022] As a further improvement to this technical solution, the working fluid expansion pressure energy recovery module includes a low-boiling-point working fluid adiabatic expansion process.

[0023] The adiabatic expansion process of the low-boiling-point working fluid will expand the high-pressure, low-temperature, low-boiling-point working fluid after transferring heat data to the heat recovery unit to low-temperature, low-pressure, converting pressure energy into cooling energy.

[0024] As a further improvement to this technical solution, the working fluid mixing and pressurization unit includes a constant pressure mixing module and an isentropic pressurization module;

[0025] The constant pressure mixing module mixes the throttled liquid working fluid and the expanded gaseous working fluid at a constant pressure ratio.

[0026] The trace amount of low-boiling-point gaseous working fluid generated after constant pressure mixing is recovered by entering the throttling flash evaporation module through the attached bypass pipeline.

[0027] The isentropic pressurization module pressurizes the mixed working fluid through the working fluid pump module and sends the pressurized mixed working fluid into the heat exchange module for further heat exchange, thus completing the advanced thermodynamic cycle.

[0028] As a further improvement to this technical solution, the monitoring and control unit includes an intelligent optimization unit and a coordination and control unit;

[0029] The intelligent optimization unit includes a state prediction module, an efficiency optimization module, and a feedback control module.

[0030] The state prediction module predicts the phase changes of the mixed organic working fluid during the isobaric endothermic process based on a thermodynamic model according to the real-time changes of the heat source; it also predicts the phase changes of the working fluid in the throttling flash evaporation module in real time to determine the evaporation rate of low-boiling-point components; and it predicts the thermodynamic properties of the working fluid through a regression model to adjust the heat exchange process and pressurization strategy.

[0031] The efficiency optimization module, through Analysis was conducted, the opening degree of the throttling module was adjusted, and a viscosity correction factor and a friction factor affected by deposits on the inner surface of the pipe were introduced. The analysis formula is optimized to preferentially evaporate low-boiling-point components; the pressure ratio and load of the adiabatic compression module and adiabatic expansion module are adjusted through a genetic algorithm; and the operating parameters of the heat exchanger are adjusted according to the real-time working fluid flow rate and temperature.

[0032] The feedback control module monitors the ratio of the working fluid in the mixing tank and the pressure of the booster pump in the working fluid mixing and pressurization unit, and adjusts the operating status of the pump module in real time.

[0033] The coordination and control unit includes a flash evaporation and compression linkage control module, an expansion and mixing synchronization optimization module, and a waste heat recovery process coordination module.

[0034] The flash evaporation and compression linkage control module is based on the prediction of working fluid phase change, monitors the mass fraction of the gaseous working fluid in the flash evaporation module in real time, and dynamically adjusts the operating status of the adiabatic compression module according to the mass fraction based on the model prediction control algorithm.

[0035] The waste heat recovery process coordination module monitors the heat transfer efficiency of each heat exchange module based on the feedback control module and adjusts the flow rate and temperature of the cooling medium.

[0036] The expansion and mixing synchronization optimization module monitors the power output of the adiabatic expansion module, the temperature and pressure of the working fluid based on the efficiency optimization module, and adjusts them synchronously with the ratio of the working fluid in the mixing tank.

[0037] The waste heat recovery process coordination module monitors the heat transfer efficiency of each heat exchange module based on the feedback control module and adjusts the flow rate and temperature of the cooling medium.

[0038] As a further improvement to this technical solution, the... Analysis:

[0039]

[0040] Among them, E sf Indicates the working fluid Change; m sf C represents the mass flow rate of the working fluid; sf T represents the average specific heat capacity of the working fluid. sf T0 represents the temperature of the working fluid after throttling; T0 represents the ambient temperature.

[0041] The viscosity of a fluid affects flow resistance and heat transfer characteristics. Based on the fluid's viscosity, flow velocity, and Reynolds number, a viscosity correction factor α is established. u :

[0042]

[0043] Where β represents the viscosity of the fluid; k represents a constant correction factor (adjusted according to the type of fluid and flow conditions); v represents the flow velocity; d represents the pipe diameter; and Re represents the Reynolds number.

[0044] Deposits increase the surface roughness of the pipe, and corrections are made to the roughness of the inner surface of the pipe. The thickness of the deposits is expressed as the thickness of the deposition layer between the fluid and the pipe surface.

[0045] θ eff =θ or +γ s ;

[0046] Where, θ eff θ represents the effective surface roughness after considering sediments. or Indicates the original roughness of the pipe before deposits; γ s Indicates sediment thickness;

[0047] Deposits increase the roughness of the inner surface of the pipe, and the friction factor f ro Correction based on effective roughness:

[0048]

[0049] Viscosity correction factor α u and the friction factor f affected by deposits on the inner surface of the pipe ro Introduction Optimize the analysis formula:

[0050]

[0051] Among them, E sf1 Indicates the optimized working fluid change.

[0052] As a further improvement to this technical solution, the step of dynamically adjusting the operating state of the adiabatic compression module based on the model predictive control algorithm according to the mass fraction includes the following steps:

[0053] S3.1 Real-time monitoring of the mass fraction of the gaseous working fluid in the flash evaporation module, and transmitting the mass fraction as a feedback signal to the control system;

[0054] S3.2 Determine the target gas phase mass fraction;

[0055] S3.3 Based on the current gas phase mass fraction and compressor pressure, predict the future state through model predictive control algorithm, establish optimization problem formula to optimize control input, and introduce gas-liquid separation efficiency parameter into the optimization problem formula of predictive control algorithm for optimization;

[0056] S3.4. Based on the optimization results of the model predictive control algorithm, dynamically adjust the operating status of the compressor.

[0057] As a further improvement to this technical solution, in S3.3, the optimization problem formula is as follows:

[0058]

[0059] Where r(t) represents the control input variable; w ga (i) represents the actual gas phase mass fraction at step i; w gat (i) represents the gas phase mass fraction of the target at step i; Pco (i) represents the actual output pressure of the adiabatic compression module at step i; P cot (i) represents the output pressure of the target adiabatic compression module at step i; Q represents the weighted matrix of the output pressure error of the adiabatic compression module; R represents the weighted matrix of the output pressure error of the adiabatic compression module; i represents the index of the prediction time domain; t represents time; N represents the length of the prediction time domain.

[0060] Considering the impact of gas-liquid separation efficiency in the flash evaporation module on the quality of the compressor input gas, a gas-liquid separation efficiency parameter is introduced into the optimization formula of the predictive control algorithm for optimization:

[0061] The gas-liquid separation efficiency d(t) is included as another control variable in the optimization problem formula to penalize the negative impact of low separation efficiency:

[0062]

[0063] Where d1(t) represents the target gas-liquid separation efficiency; denoted by ; A represents the weighting matrix of separation efficiency error.

[0064] On the other hand, the present invention provides a method for recovering and utilizing ultra-low temperature heat energy based on an advanced thermodynamic cycle, used in the aforementioned ultra-low temperature heat energy recovery and utilization system based on an advanced thermodynamic cycle, comprising the following steps:

[0065] S4.1 Pre-treat the low-temperature heat source and transmit the heat data to the working fluid through the heat exchange module;

[0066] S4.2 Receive heat data and perform heat data conversion and working fluid compression;

[0067] S4.3, Combining the Rankine cycle to transfer heat energy to do work;

[0068] S4.4, The pressure energy is converted into cooling energy through the adiabatic expansion pressure energy recovery module;

[0069] S4.5. Mix working fluids in different states and pressurize the mixed working fluids;

[0070] S4.6. Through intelligent optimization and coordinated control, predict, adjust and optimize each process of the heat recovery system in real time.

[0071] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0072] 1. In the ultra-low temperature heat energy recovery and utilization system and method based on advanced thermodynamic cycles, by adopting advanced thermodynamic cycles, especially the efficient energy conversion mechanism in the ultra-low temperature range, the waste low-temperature heat energy can be recovered and utilized to the maximum extent. In refrigeration engineering, a portion of the heat that needs to be removed is recovered and used for work, replacing part of the external power supply, thus minimizing the external power supply, the total waste energy and cooling water consumption, thereby achieving the goal of energy saving and emission reduction, and further reducing the limit of low-temperature heat energy utilization in refrigeration engineering. The COP of ultra-low temperature heat energy utilization refrigeration engineering using mixed working fluid thermodynamic cycles can reach above 7.0.

[0073] 2. In ultra-low temperature heat energy recovery and utilization systems and methods based on advanced thermodynamic cycles, the application of advanced thermodynamic cycle technology in the recovery process of low-temperature waste heat can reduce energy consumption dependent on traditional fuels, thereby reducing the emission of greenhouse gases and harmful pollutants. This not only helps promote the green transformation of the energy structure, but also has important significance for mitigating global climate change and improving air quality. Attached Figure Description

[0074] Figure 1 This is an overall flowchart of the present invention;

[0075] Figure 2 This is a schematic diagram of the advanced thermodynamic cycle of the present invention;

[0076] The meanings of the labels in the diagram are as follows:

[0077] 1. Heat source guidance and heat absorption unit; 11. Heat source pretreatment module; 12. Constant pressure heat absorption module; 2. Heat energy conversion and working fluid compression unit; 21. Throttling flash evaporation module; 22. Adiabatic compression module; 23. Working fluid expansion pressure energy recovery module; 3. Heat recovery and heat release unit; 4. Working fluid mixing and pressurization unit; 41. Constant pressure mixing module; 42. Isentropic pressurization module; 5. Monitoring and control unit; 51. Intelligent optimization unit; 511. State prediction module; 512. Efficiency optimization module; 513. Feedback control module; 52. Coordination and control unit; 521. Flash evaporation and compression linkage control module; 522. Expansion and mixing synchronous optimization module; 523. Waste heat recovery process coordination module. Detailed Implementation

[0078] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0079] Example 1: Please refer to Figure 1 As shown, an ultra-low temperature heat energy recovery and utilization system based on an advanced thermodynamic cycle is provided, including:

[0080] The heat source guiding and heat absorption unit 1 pre-treats the low-temperature heat source and transmits the heat data to the working fluid through the heat exchange module (transmission principle diagram as shown in the figure). Figure 2 (as shown);

[0081] In this embodiment, the heat source guiding and heat absorption unit 1 includes a heat source pretreatment module 11 and a constant pressure heat absorption module 12;

[0082] The heat source pretreatment module 11 collects low-temperature heat sources and pretreats the low-temperature heat sources (waste heat, residual heat or ambient heat). The pretreatment process includes adjusting the temperature and pressure of the heat source to ensure that the heat source meets the operating requirements when it enters the subsequent heat exchanger. In this embodiment, the heat source pretreatment module 11 uses a heat exchanger.

[0083] The constant pressure heat absorption module 12 transfers heat from the low-temperature heat source to the mixed organic working fluid through a heat exchange module (heat exchanger). In this embodiment, the mixed organic working fluid is R600a / R245fa.

[0084] The heat energy conversion and working fluid compression unit 2 receives heat data and performs heat data conversion and working fluid compression to ensure efficient energy conversion and output;

[0085] In this embodiment, the heat energy conversion and working fluid compression unit 2 includes a throttling flash evaporation module 21, an adiabatic compression module 22, and a working fluid expansion pressure energy recovery module 23.

[0086] The throttling flash evaporation module 21 reduces the temperature and pressure of the mixed organic working fluid through isentropic throttling, and the low-boiling-point organic working fluid evaporates preferentially, thereby transferring the heat energy absorbed by the mixed organic working fluid to the low-boiling-point gas phase working fluid. In this embodiment, the throttling flash evaporation module 21 includes a throttling device and a flash tank.

[0087] The adiabatic compression module 22 pressurizes the low-boiling-point gaseous working fluid, increasing its temperature and pressure to prepare for the subsequent heat release process (boost compressor). The mixed working fluid enters the throttling device at a higher temperature and pressure. At this time, the mixed working fluid may be in a liquid phase or a gas-liquid two-phase state. The pressure of the mixed working fluid is reduced to the target pressure through the throttling module (throttling device). This process is idealized as an isentropic process. Due to the reduction in temperature and pressure, the low-boiling-point component (R600a) in the mixed working fluid evaporates preferentially, forming a gas-liquid two-phase mixture, while the high-boiling-point component (R245fa) mainly remains in the liquid phase. The gas-liquid two-phase mixture is then transferred to the flash evaporation module (flash tank), where further gas-liquid separation is achieved. The gas phase is collected and sent to the compressor for subsequent processing, while the liquid phase is sent to the working fluid mixing and pressurization unit for recycling. In this embodiment, the adiabatic compression module 22 uses a boost compressor to transfer heat data to the heat recovery and heat release unit 3.

[0088] The working fluid expansion pressure energy recovery module 23 adiabatically expands the high-pressure, low-temperature working fluid to further reduce its temperature and pressure, providing cooling energy to the system. In this process, an expander is used to convert pressure energy into cooling or mechanical energy. The two-phase screw expander performs work externally, reducing the temperature and pressure of the saturated working fluid. The working fluid expansion pressure energy recovery module 23 includes a low-boiling-point working fluid adiabatic expansion process. The low-boiling-point working fluid adiabatic expansion process expands the high-pressure, low-temperature, low-boiling-point working fluid, after transferring heat data to the heat recovery unit, to a low-temperature, low-pressure state, converting pressure energy into cooling energy.

[0089] Heat recovery and heat release unit 3 includes a constant pressure heat exchanger and an additional Rankine cycle system;

[0090] The heat recovery and heat release unit 3 includes a low-boiling-point working fluid in a constant-pressure heat exchange module that transfers heat data to an external Rankine cycle working fluid through partial condensation.

[0091] The heat recovery and heat release unit 3 includes constant-pressure heat exchange in a constant-pressure heat exchange module to reduce the temperature of the working fluid and transmit heat data to the Rankine cycle working fluid.

[0092] The heat recovery and heat release unit 3 includes the use of an additional Rankine cycle working fluid to perform work externally;

[0093] In this embodiment, the heat recovery and heat release unit 3 transfers the working fluid from the outlet of the adiabatic compression module 22 to the heat release module. At this time, the working fluid is usually in a high temperature and high pressure state. In this embodiment, the heat release module adopts a heat exchanger.

[0094] In the heat release module, the working fluid exchanges heat at constant pressure with the external Rankine cycle working fluid (external organic working fluid, etc.) through the heat exchange module (heat exchanger). Heat is transferred from the working fluid to the Rankine cycle working fluid. The heat release process usually reduces the temperature and pressure of the working fluid. The state of the working fluid gradually changes from high temperature gas (or gas-liquid mixture) to low temperature liquid (or low saturated gas).

[0095] In a heat exchanger, the working fluid typically undergoes partial condensation, releasing latent heat. This released heat is transferred to the Rankine cycle working fluid via a heat exchange module for heating or performing work, thereby improving the system's energy efficiency. In this embodiment, a heat exchanger is used as the heat exchange module.

[0096] The thermal expansion module 23 expands the high-pressure, low-temperature working fluid to a low-temperature, low-pressure state.

[0097] In this embodiment, the adiabatic expansion module adopts a screw expander, which converts pressure energy into cooling or mechanical energy. The two-phase screw expander performs work on the outside, reducing the temperature and pressure of the saturated working fluid.

[0098] The expansion process is a two-phase expansion. In the expander, the working fluid pressure drops to balance with the pressure of the throttling flash module, and the working fluid temperature drops below the flash temperature of the mixed working fluid.

[0099] The working fluid mixing and pressurization unit 4 mixes working fluids in different states and pressurizes the mixed working fluid to ensure the continuous operation of the system.

[0100] In this embodiment, the working fluid mixing and pressurization unit 4 includes a constant pressure mixing module 41 and an isentropic pressurization module 42;

[0101] The constant pressure mixing module 41 mixes the high-boiling-point working fluid after throttling and flash evaporation with the low-boiling-point working fluid after adiabatic expansion in a constant pressure ratio.

[0102] The isentropic pressurization module 42 pressurizes the mixed working fluid through the working fluid pump module and sends the pressurized mixed working fluid into the heat source guiding and heat absorption unit 1 to continue heat exchange, thus completing the advanced thermodynamic cycle. In this embodiment, the isentropic pressurization module uses a working fluid pump.

[0103] The monitoring and control unit 5 predicts, adjusts and optimizes each process of the heat recovery system (phase change, throttling flash, compression and expansion) in real time through intelligent optimization and coordinated control, ensuring efficient energy conversion and heat transfer, while maximizing the overall system performance and energy utilization efficiency. It also incorporates viscosity correction factors and friction factors affected by deposits on the inner surface of the pipe into the intelligent optimization process for further optimization.

[0104] In this embodiment, the monitoring and control unit 5 includes an intelligent optimization unit 51 and a coordination and control unit 52;

[0105] The intelligent optimization unit 51 includes a state prediction module 511, an efficiency optimization module 512, and a feedback control module 513.

[0106] The state prediction module 511 predicts the phase changes of the mixed organic working fluid during isobaric heat absorption based on a thermodynamic model, according to real-time changes in the heat source (waste heat source temperature, pressure, etc.). Through the prediction model, the system can optimize the adjustment of the heat source to ensure efficient heat transfer to the working fluid and improve heat exchange efficiency. It also predicts the phase changes of the working fluid in the throttling flash evaporation module 21 in real time, determines the evaporation rate of low-boiling-point components, and optimizes the throttling valve opening to ensure the maximum proportion of gaseous working fluid and reduce energy loss during subsequent compression and expansion. Furthermore, it predicts the thermodynamic properties (temperature, pressure, enthalpy) of the working fluid through a regression model, adjusts the heat exchange process and pressurization strategy, and ensures efficient heat recovery and optimal flow state of the working fluid.

[0107] The efficiency optimization module 512 passes through Analysis was conducted, and the opening degree of the throttling module (throttling device) was adjusted. A viscosity correction factor and a friction factor influenced by deposits on the inner surface of the pipe were also introduced. The system optimizes the analysis formula to preferentially evaporate low-boiling-point components and avoid waste of heat from high-boiling-point components. By optimizing the throttling flash evaporation process, unnecessary energy consumption is reduced, thereby improving the overall system's thermal energy conversion efficiency. The system uses a genetic algorithm to adjust the pressure ratio and load of the adiabatic compression module 22 and the adiabatic expansion module 23 to make the system's energy conversion process more efficient, avoiding excessive power consumption caused by over-compression or expansion and maximizing energy recovery during compression and expansion. Furthermore, the system adjusts the heat exchanger's operating parameters, such as heat exchange area and flow rate, based on real-time working fluid flow rate and temperature to ensure efficient heat transfer from the working fluid to the external cooling medium.

[0108] Furthermore, Analysis:

[0109]

[0110] Among them, E sf Indicates the working fluid Change; m sf C represents the mass flow rate of the working fluid; sf T represents the average specific heat capacity of the working fluid. sf T0 represents the temperature of the working fluid after throttling; T0 represents the ambient temperature.

[0111] Fluid viscosity affects flow resistance and heat transfer characteristics. In throttling flash evaporation and heat exchange processes, the effect of viscosity on flow influences the efficiency of heat conduction, thus affecting thermal energy changes. Therefore, fluid viscosity is introduced as a correction factor. In the analytical formula, the viscosity of the fluid usually affects the fluid's thermal conductivity, flow state (laminar flow, turbulent flow), and friction loss between the fluid and the pipe surface;

[0112] The viscosity of a fluid affects flow resistance and heat transfer characteristics. Based on the fluid's viscosity, flow velocity, and Reynolds number, a viscosity correction factor α is established. u Generally speaking, increased viscosity leads to turbulent flow losses and reduced heat transfer efficiency. Therefore, the formula for heat energy change can be modified based on the actual flow state of the fluid.

[0113]

[0114] Where β represents the viscosity of the fluid; k represents a constant correction factor (adjusted according to the type of fluid and flow conditions); v represents the flow velocity; d represents the pipe diameter; and Re represents the Reynolds number.

[0115] Deposits increase the surface roughness of pipes and correct for the roughness of the inner surface. The thickness of the deposits represents the thickness of the deposit layer between the fluid and the pipe surface. (Deposits increase the roughness of the inner surface of the pipe, leading to increased friction between the fluid and the pipe wall. This frictional loss reduces the overall efficiency of the system, especially in heat recovery systems, because higher frictional losses result in more energy being converted into heat and consumed rather than used for efficient heat transfer. Deposits can also cause changes in the fluid flow state. For example, at lower flow rates, the flow may remain laminar, while at higher flow rates, turbulence may occur. Because rough surfaces affect the interaction between the fluid and the pipe wall, deposits make the flow more unstable, potentially altering the Reynolds number and causing changes in the flow state. This change affects flow resistance, turbulence generation, and heat transfer efficiency; deposits inside the pipe increase thermal resistance, especially during heat exchange. The deposit layer reduces the effective contact between the fluid and the pipe wall, reducing heat transfer efficiency. As the deposit thickness increases, heat conduction and convection through the pipe wall are hindered, thus affecting the heat recovery effect.)

[0116] θ eff =θ or +γ s ;

[0117] Where, θ eff θ represents the effective surface roughness after considering sediments. or Indicates the original roughness of the pipe before deposits; γ s Indicates sediment thickness;

[0118] Deposits increase the roughness of the inner surface of the pipe, and the friction factor f roCorrections are made based on effective roughness (as deposits accumulate on the inner surface of the pipe, surface roughness increases, leading to increased friction between the fluid and the pipe wall. During flow, the fluid is dragged by the rough surface of the pipe wall (deposits, scale, etc.), thus generating additional frictional resistance):

[0119]

[0120] Viscosity correction factor α u and the friction factor f affected by deposits on the inner surface of the pipe ro Introduction Optimize the analysis formula (by adjusting the viscosity correction factor α) u and the friction factor f affected by deposits on the inner surface of the pipe ro Introducing these factors into the formula allows for a comprehensive consideration of the fluid's physical properties (such as viscosity) and the system's structural variations (such as pipe surface roughness and deposit effects), thereby optimizing the calculation of the heat recovery process.

[0121]

[0122] Among them, E sf1 Indicates the optimized working fluid change.

[0123] The feedback control module 513 monitors the ratio of the working fluid in the mixing tank of the working fluid mixing and pressurizing unit 4 and the pressure of the pressurizing pump, and adjusts the operating status of the pump module (regulating pump) in real time to ensure the best efficiency of working fluid flow and heat exchange.

[0124] The coordination and control unit 52 includes a flash evaporation and compression linkage control module 521, an expansion and mixing synchronization optimization module 522, and a waste heat recovery process coordination module 523.

[0125] The flash evaporation and compression linkage control module 521 is based on the prediction of working fluid phase change, monitors the mass fraction of gaseous working fluid in the flash evaporation module (flash tank) in real time, and dynamically adjusts the operating status of the adiabatic compression module 22 according to the mass fraction based on the model prediction control algorithm. Through linkage control, it ensures that the compressor boost ratio is adapted to the needs of subsequent stages and avoids excessive or insufficient compression that leads to energy loss or unnecessary power consumption.

[0126] By monitoring the mass fraction of the gaseous working fluid in real time and adjusting the compressor's operating parameters accordingly, the compression process can be ensured to always operate under optimal conditions, avoiding unnecessary energy consumption and significantly improving the overall system's thermal energy conversion efficiency. The model predictive control algorithm can quickly respond to changes in heat source and operating conditions, and promptly adjust the compressor's operating parameters, such as speed and load, making the system more flexible in responding to different operating conditions and maintaining a highly efficient operating state. Dynamically adjusting the compressor's boost ratio and load can avoid energy waste caused by over-compression or expansion, maximize energy recovery during compression and expansion, and further improve energy utilization.

[0127] The operating status of the adiabatic compression module 22 is dynamically adjusted based on the mass fraction using a model predictive control algorithm, including the following steps:

[0128] S3.1 Real-time monitoring of the mass fraction of the gaseous working fluid in the flash module (flash tank) and transmission of the mass fraction as a feedback signal to the control system;

[0129] S3.2 Determine the target gas phase mass fraction;

[0130] S3.3 Based on the current gas phase mass fraction and compressor pressure, predict the future state through model predictive control algorithm, establish optimization problem formula to optimize control input, and introduce gas-liquid separation efficiency parameter into the optimization problem formula of predictive control algorithm for optimization. The optimization goal is to make the gas phase mass fraction and compressor output pressure as close as possible to the desired target value.

[0131] Furthermore, the optimization problem formula is as follows:

[0132]

[0133] Where r(t) represents the control input variable, such as the rotational speed or power of the adiabatic compression module 22; N represents the number of time steps considered by the optimization algorithm; wga(i) represents the actual gas phase mass fraction at step i; wgat(i) represents the target gas phase mass fraction at step i; P co (i) represents the actual output pressure of the adiabatic compression module 22 at step i; P cot (i) represents the output pressure of the target adiabatic compression module 22 at step i; Q represents the weighted matrix of the output pressure error of the adiabatic compression module 22; R represents the weighted matrix of the output pressure error of the adiabatic compression module 22; i represents the index of the prediction time domain; t represents time; N represents the length of the prediction time domain, which means that when the control system performs optimization calculations, it will predict the system behavior in the future for a period of time. During this period of time, the control input will be optimized to meet the predetermined target and constraints.

[0134] Considering the impact of gas-liquid separation efficiency in the flash evaporation module on the mass of the compressor input gas, a gas-liquid separation efficiency parameter is introduced into the optimization formula of the predictive control algorithm for optimization. (The core function of the flash evaporation module is to separate the mixed working fluid into gas and liquid phases at different temperatures and pressures. The effectiveness of this process directly determines the mass flow rate of the gaseous working fluid entering the compressor. Efficient gas-liquid separation reduces the carryover of liquid working fluid, thus ensuring that the main working fluid entering the compressor is gas. When the gas-liquid separation efficiency is low, more liquid working fluid will enter the compressor, which will cause the compressor to process more incompressible liquids, increase compression power consumption, and reduce the overall energy efficiency of the system. Therefore, incorporating gas-liquid separation efficiency into the optimization algorithm can avoid the energy loss caused by inefficient separation.)

[0135] The gas-liquid separation efficiency d(t) is included as another control variable in the optimization problem formula to penalize the negative impact of low separation efficiency:

[0136]

[0137] Where d1(t) represents the target gas-liquid separation efficiency; represents the penalty coefficient, used to weigh the importance of the gas-liquid separation efficiency error term; A represents the weighting matrix of the separation efficiency error.

[0138] For the gas-liquid separation efficiency d(t), a recursive formula is designed (the operation of a thermodynamic cycle system is time-varying, and the state of the working fluid changes over time. Especially in the heat recovery process, the gas-liquid separation efficiency is affected by variables such as fluid temperature, pressure, and mass flow rate, and these variables themselves change with time and system state. Therefore, using a recursive formula can capture this time-varying nature; the recursive formula helps to adjust system parameters in real time. For example, by considering the change in separation efficiency at the previous moment, the operating state of the flash evaporation module can be dynamically adjusted to maintain the stability and efficiency of the system. Through recursion, the operating decision at the next moment can be based not only on the current input, but also on past trends and states, which is crucial for real-time adjustment):

[0139]

[0140] Where δ1 represents the inertia of separation efficiency over time; δ2 represents the effect of gas flow rate on separation efficiency; δ3 represents the effect of temperature difference on separation efficiency; mg(t) represents the gas flow rate at step t; mt(t) represents the total flow rate (gas + liquid) at step t; Te(t) represents the ambient temperature at step t; and T0 represents the reference temperature, which is the ambient temperature or the reference temperature under system operating conditions.

[0141] S3.4. Based on the optimization results of the model predictive control algorithm, dynamically adjust the operating status of the compressor (adjust the compressor speed, power, etc.) to ensure efficient system operation.

[0142] The expansion and mixing synchronization optimization module 522 monitors the power output of the adiabatic expansion module 23, the temperature and pressure of the working fluid based on the efficiency optimization module 512, and adjusts them synchronously with the ratio of the working fluid in the mixing tank. By ensuring that the power of the expansion process is consistent with the ratio of the mixing working fluid, the system can ensure the maximum constant pressure mixing effect and effectively improve the heat recovery efficiency.

[0143] The waste heat recovery process coordination module 523 monitors the heat transfer efficiency of each heat exchange module (heat exchanger) based on the feedback control module 513. According to the real-time feedback, it adjusts the flow rate and temperature of the cooling medium to ensure that the heat exchanger works at the best efficiency, avoids overheating or overcooling, improves heat transfer efficiency, and reduces heat waste.

[0144] Example 2: Please refer to Figure 2 As shown, an ultra-low temperature heat energy recovery and utilization system based on advanced thermodynamic cycles is provided, including a 100kW computing power data center cooling system as an example to illustrate the beneficial effects of the present invention:

[0145] In this embodiment, a data center cooling system with a computing power consumption of 100kW is used as an example to establish a data center cooling model based on an advanced thermodynamic cycle, with the heat source temperature being approximately 45-60°C (the temperature of the hot air in the computer room).

[0146] Let the total power consumption of the computing device be Nt = 100 kW.

[0147] Therefore, the total heat transferred is Qt = η1·x·η2·x·η3·Nt = 80 (kW).

[0148] In the formula: Qt is the heat load of the computer equipment;

[0149] Nt represents the total power consumption of the computing device (auxiliary power consumption is not considered for the sake of simplifying the problem);

[0150] η1 is the coefficient for simultaneous use;

[0151] η2 is the utilization coefficient;

[0152] η3 is the load uniformity coefficient;

[0153] Typically, η1, η2, and η3 are taken between 0.6 and 0.8. Considering the redundancy of cooling capacity, the upper limit of η1, η2, and η3 is usually taken as 0.8.

[0154] Therefore, the system cooling capacity requirement is 80kW, which means the heat transfer of the mixed working fluid is 80kW.

[0155] Assume the working fluid in the advanced thermodynamic cycle cryogenic heat recovery system is R600a / R245fa with a mixing ratio of 15:85. Then the specific heat capacity of the working fluid is 1.45 KJ / kg·K, the density of the gaseous working fluid R600a is 1.19 m³ / kg, the temperature rise in the plate evaporator is 20℃, the isentropic efficiency of the compressor is 0.8, and the dryness fraction of the working fluid in the two-phase flow expander is 0.3 with an isentropic efficiency of 0.75. Therefore:

[0156] In a plate heat exchanger, the flow rate of the mixed working fluid should be 9.91 t / h;

[0157] The gas phase mass flow rate after throttling and flash evaporation is 766 kg / h, which is 644 m³ / h or 0.22 kg / s. The calculated power consumption of the compressor is 766 x 88.2 = 67561 kJ / h = 18.7 kW, and the actual power consumption is approximately 23.4 kW.

[0158] The output power of the R600a expander is: 766 x 233 = 178478 kJ / h = 49.6 kW, and the actual output power is approximately 37.1 kW.

[0159] Furthermore, assuming the auxiliary Rankine cycle working fluid is a single working fluid R245fa, the expander working fluid dryness fraction is 0.6, and the expander isentropic efficiency is 0.8, then...

[0160] In the two-stage plate heat exchanger, the working fluid flow rate is 503 kg / h;

[0161] The output power of the R245fa expander is 503 x 38 = 19128 kJ / h = 5.3 kW, and the actual power is approximately 4.25 kW.

[0162] Therefore, the external power Ns supplied by the system should be: Ns = 23.4 - 37.1 - 4.25 = -17.95 kW.

[0163] The system's heat discharge is 88025 kJ / h;

[0164] External cooling water supply capacity: 22 t / h;

[0165] Compared to traditional refrigeration methods:

[0166] The system's external power supply is 40kW (PUE is calculated as 1.4);

[0167] The system's heat discharge is 360,000 KJ / h;

[0168] External cooling water supply capacity: 90 t / h;

[0169] Here, Ns represents the actual external power supply: -17.95 (kW).

[0170] System PUE: PUE = 1 + (-17.95) / 100kW = 0.82;

[0171] Overall system The efficiency is: 0.227 / 1.173 = 19.35%;

[0172] The system performance coefficient (COP) is as high as 7.04.

[0173] The difference between Embodiment 2 and Embodiment 1 is that Embodiment 1 introduces the advanced thermodynamic cycle method used in the ultra-low temperature heat energy recovery and utilization system based on the advanced thermodynamic cycle, while Embodiment 2 is a specific application example of the ultra-low temperature heat energy recovery and utilization system based on the advanced thermodynamic cycle.

[0174] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A cryogenic heat energy recovery and utilization system based on advanced thermodynamic cycles, characterized in that, include: The heat source guiding and heat absorption unit (1) pre-treats the low-temperature heat source and transmits the heat data to the mixed organic working fluid through the heat exchange module; The heat energy conversion and working fluid compression unit (2) receives heat data and performs heat data conversion and working fluid compression. The heat recovery and heat release unit (3) reduces the temperature of the working fluid through constant pressure heat exchange and transmits the heat data to the Rankine cycle to do work. The working fluid expansion pressure energy recovery module (23) performs adiabatic expansion of the high-pressure and low-temperature working fluid to further reduce the temperature and pressure of the working fluid and provide cooling energy to the system. The working fluid mixing and pressurization unit (4) mixes working fluids in different states and pressurizes the mixed working fluid; The monitoring and control unit (5) predicts, adjusts and optimizes each process of the heat recovery system in real time through intelligent optimization and coordinated control, and introduces the viscosity correction factor and the friction factor affected by the deposits on the inner surface of the pipe into the intelligent optimization process for further optimization.

2. The ultra-low temperature heat energy recovery and utilization system based on advanced thermodynamic cycle according to claim 1, characterized in that: The heat source guiding and heat absorption unit (1) includes a heat source pretreatment module (11) and a constant pressure heat absorption module (12); The heat source pretreatment module (11) collects low-temperature heat sources and pretreatments them. The constant pressure heat absorption module (12) transfers heat from the low-temperature heat source to the mixed organic working fluid through the heat exchange module.

3. The ultra-low temperature heat energy recovery and utilization system based on advanced thermodynamic cycle according to claim 2, characterized in that: The heat energy conversion and working fluid compression unit (2) includes a throttling flash evaporation module (21) and an adiabatic compression module (22); The throttling flash evaporation module (21) reduces the temperature and pressure of the mixed organic working fluid through isentropic throttling, so that the heat energy absorbed by the mixed organic working fluid is transferred to the low-boiling-point working fluid, thereby promoting the vaporization of the low-boiling-point working fluid. The adiabatic compression module (22) pressurizes the low-boiling-point gaseous working fluid, increases the temperature and pressure of the low-boiling-point gaseous working fluid, and transfers heat data to the heat recovery and heat release unit (3).

4. The ultra-low temperature heat energy recovery and utilization system based on advanced thermodynamic cycle according to claim 3, characterized in that: The heat recovery and heat release unit (3) includes a constant pressure heat exchanger and an additional Rankine cycle system; The heat recovery and heat release unit (3) includes a low-boiling-point working fluid in a constant-pressure heat exchange module that transfers heat data to an external Rankine cycle working fluid through partial condensation. The heat recovery and heat release unit (3) includes constant pressure heat exchange in the constant pressure heat exchange module to reduce the temperature of the working fluid and transmit heat data to the Rankine cycle working fluid; The heat recovery and heat release unit (3) includes performing work externally using an additional Rankine cycle working fluid.

5. The ultra-low temperature heat energy recovery and utilization system based on advanced thermodynamic cycle according to claim 4, characterized in that: The working fluid expansion pressure energy recovery module (23) includes a low-boiling-point working fluid adiabatic expansion process; The adiabatic expansion process of the low-boiling-point working fluid expands the high-pressure, low-temperature, low-boiling-point working fluid, after transferring heat data to the heat recovery unit, to a low-temperature, low-pressure state, converting pressure energy into cooling energy.

6. The ultra-low temperature heat energy recovery and utilization system based on advanced thermodynamic cycle according to claim 5, characterized in that: The working fluid mixing and pressurization unit (4) includes a constant pressure mixing module (41) and an isentropic pressurization module (42); The constant pressure mixing module (41) mixes the throttled low-temperature, low-pressure, high-boiling-point liquid working fluid with the expanded low-temperature, low-pressure, two-phase low-boiling-point working fluid at constant pressure. The trace amount of low-boiling-point gaseous working fluid generated after constant pressure mixing is recovered by entering the throttling flash evaporation module through the attached bypass pipeline. The isentropic pressurization module (42) pressurizes the mixed working fluid through the working fluid pump module and sends the pressurized mixed working fluid into the heat exchange module to continue heat exchange, thus completing the advanced thermodynamic cycle.

7. The ultra-low temperature heat energy recovery and utilization system based on advanced thermodynamic cycle according to claim 6, characterized in that: The monitoring and control unit (5) includes an intelligent optimization unit (51) and a coordination and control unit (52); The intelligent optimization unit (51) includes a state prediction module (511), an efficiency optimization module (512), and a feedback control module (513). The state prediction module (511) predicts the phase change of the mixed organic working fluid during the isobaric endothermic process based on the real-time changes of the heat source and the thermodynamic model; it also predicts the phase change of the working fluid in the throttling flash evaporation module (21) in real time, determines the evaporation amount of low-boiling-point components, and adjusts the heat exchange process and pressurization strategy by predicting the thermodynamic properties of the working fluid through a regression model. The efficiency optimization module (512) through Analysis was conducted, the opening degree of the throttling module was adjusted, and a viscosity correction factor and a friction factor affected by deposits on the inner surface of the pipe were introduced. The analysis formula is optimized to allow low-boiling-point components to evaporate preferentially; the pressure ratio and load of the adiabatic compression module (22) and the adiabatic expansion module are adjusted by a genetic algorithm; and the operating parameters of the heat exchanger are adjusted according to the real-time working fluid flow rate and temperature. The feedback control module (513) adjusts the operating status of the pump module in real time by monitoring the ratio of the working medium in the mixing tank and the pressure of the booster pump in the working medium mixing and pressurizing unit (4). The coordination and control unit (52) includes a flash evaporation and compression linkage control module (521), an expansion and mixing synchronization optimization module (522), and a waste heat recovery process coordination module (523). The flash evaporation and compression linkage control module (521) monitors the mass fraction of the gaseous working fluid in the flash evaporation module in real time based on the prediction of the phase change of the working fluid, and dynamically adjusts the operating status of the adiabatic compression module (22) according to the mass fraction based on the model prediction control algorithm. The waste heat recovery process coordination module (523) monitors the heat transfer efficiency of each heat exchange module based on the feedback control module (513) and adjusts the flow rate and temperature of the cooling medium. The expansion and mixing synchronization optimization module (522) monitors the power output of the adiabatic expansion module, the temperature and pressure of the working fluid based on the efficiency optimization module (512), and adjusts them synchronously with the working fluid ratio in the mixing tank.

8. The ultra-low temperature heat energy recovery and utilization system based on advanced thermodynamic cycle according to claim 7, characterized in that, The Analysis: Among them, E sf Indicates the working fluid Change; m sf C represents the mass flow rate of the working fluid; sf T represents the average specific heat capacity of the working fluid. sf T0 represents the temperature of the working fluid after throttling; T0 represents the ambient temperature. The viscosity of a fluid affects flow resistance and heat transfer characteristics. Based on the fluid's viscosity, flow velocity, and Reynolds number, a viscosity correction factor α is established. u : Where β represents the fluid's intrinsic viscosity; k represents the constant correction factor; v represents the flow velocity; d represents the pipe's inner diameter; and Re represents the Reynolds number. Deposits increase the surface roughness of the pipe, and corrections are made to the roughness of the inner surface of the pipe. The thickness of the deposits is expressed as the thickness of the deposition layer between the fluid and the pipe surface. i eff =θ or +g s ; Where, θ eff θ represents the effective surface roughness after considering sediments. or Indicates the original roughness of the pipe before deposits; γ s Indicates sediment thickness; Deposits increase the roughness of the inner surface of the pipe, and the friction factor f ro Correction based on effective roughness: Viscosity correction factor α u and the friction factor f affected by deposits on the inner surface of the pipe ro Introduction Optimize the analysis formula: Among them, E sf1 Indicates the optimized working fluid change.

9. The ultra-low temperature heat energy recovery and utilization system based on advanced thermodynamic cycle according to claim 8, characterized in that: The flash evaporation and compression linkage control module (521) dynamically adjusts the operating state of the adiabatic compression module (22) based on the mass fraction and a model predictive control algorithm, including the following steps: S3.1 Real-time monitoring of the mass fraction of the gaseous working fluid in the flash evaporation module, and transmitting the mass fraction as a feedback signal to the control system; S3.2 Determine the target gas phase mass fraction; S3.3 Based on the current gas phase mass fraction and compressor pressure, predict the future state through model predictive control algorithm, establish optimization problem formula to optimize control input, and introduce gas-liquid separation efficiency parameter into the optimization problem formula of predictive control algorithm for optimization; S3.

4. Based on the optimization results of the model predictive control algorithm, dynamically adjust the operating status of the compressor.

10. The ultra-low temperature heat energy recovery and utilization system based on advanced thermodynamic cycle according to claim 9, characterized in that: In S3.3, the optimization problem formula is: Where r(t) represents the control input variable; wga(i) represents the actual gas phase mass fraction at step i; w gat (i) represents the gas phase mass fraction of the target at step i; P co (i) represents the actual output pressure of the adiabatic compression module (22) at step i; P cot (i) represents the output pressure of the target adiabatic compression module (22) at step i; Q represents the weighted matrix of the output pressure error of the adiabatic compression module (22); R represents the weighted matrix of the output pressure error of the adiabatic compression module (22); i represents the index of the prediction time domain; t represents time; N represents the length of the prediction time domain; Considering the impact of gas-liquid separation efficiency in the flash evaporation module on the quality of the compressor input gas, a gas-liquid separation efficiency parameter is introduced into the optimization formula of the predictive control algorithm for optimization: The gas-liquid separation efficiency d(t) is included as another control variable in the optimization problem formula to penalize the negative impact of low separation efficiency: Where d1(t) represents the target gas-liquid separation efficiency; denoted by ; A represents the weighting matrix of separation efficiency error.

11. A method for recovering and utilizing ultra-low temperature thermal energy based on an advanced thermodynamic cycle, used in the ultra-low temperature thermal energy recovery and utilization system based on an advanced thermodynamic cycle as described in any one of claims 1-10, characterized in that, Includes the following steps: S4.1 Pre-treat the low-temperature heat source and transmit the heat data to the working fluid through the heat exchange module; S4.2 Receive heat data and perform heat data conversion and working fluid compression; S4.3, Combining the Rankine cycle to transfer heat energy to do work; S4.4, The pressure energy is converted into cooling energy through the adiabatic expansion pressure energy recovery module; S4.

5. Mix working fluids in different states and pressurize the mixed working fluids; S4.

6. Through intelligent optimization and coordinated control, predict, adjust and optimize each process of the heat recovery system in real time.

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